1. Field of the Invention
The present invention relates to an image switching apparatus capable of switching and outputting a desired video signal from inputted video signals of a plurality of channels and which is also able to perform effects on the video signal upon switching, and particularly to an image switching apparatus in which circuits can be used usefully without waste in response to a variety of purposes.
2. Description of the Related Art
An image switching apparatus (switcher) has hitherto been known as one of professional apparatus for use in editing images in television broadcasting and the like. The image switching apparatus is able to switch and output a desired video signal from inputted video signals of a plurality of channels (video signals from a suitable video source such as a video camera and a VCR (video cassette recorder) and this image switching apparatus is also able to perform effects, such as wipe and mix, on a video signal upon switching. An output video signal from the image switching apparatus is supplied to equipment for transmitting audio-video programs, a video recording and reproducing apparatus, a monitor and the like.
In video edit work, it is customary to carry out various works such as to generate a video signal of only one channel or to generate video signals of a plurality of channels at the same time. Concurrently therewith, it is requested that the image switching apparatus should become available in a variety of purposes.
FIG. 1 of the accompanying drawings is a schematic block diagram showing an example of an arrangement of an image switching apparatus having such function according to the related art. As shown in FIG. 1, this previously-proposed image switching apparatus includes a plurality of image processing portions 51 (51a to 51d) in which an output video signal of one image processing unit 51 is inputted again to other image processing unit 51 as an input video signal. Each image processing unit 51 includes an input selecting unit 52 and a synthesis processing unit 55. The input selecting unit 52 includes a matrix-like selection switch group to connect respective input lines 53a to 53j to input buses 54a to 54c and video signals of one channel each can be selected by the input buses 54a to 54c. A video signal selected by the input selecting unit 52 is supplied to the synthesis processing unit 55, in which it is processed by effects such as wipe and mix and the thus processed video signal is outputted from an output signal output. Also, the above-mentioned thus processed signal from the synthesis processing unit 55 is inputted again to other image processing unit 51 from the input lines 53g to 53j (see Cited Patent Reference 1, for example).
In this image switching apparatus, when the input lines 53g to 53j (output video signals of other image processing units 51) are selected by the input selecting unit 52 of the image processing unit 51, the image processing units 51 are used in the state in which the image processing units 51 of a plurality of stages are connected in series and it becomes possible to generate a video signal of one channel on which effects of a plurality of stages were performed (to output the video signal of one channel from the output terminal output of the image processing unit 51 of the final stage).
Also, the input lines 53g to 53j are not selected by the input selecting unit 52 of the image processing unit 51 so that it becomes possible to generate video signals of a plurality of channels on which effects were performed (to output the video signals of a plurality of channels from the output terminal output of each image processing unit 51).
Cited Patent Reference 1: Official Gazette of Japanese laid-open patent application No. 2004-153486 (paragraph Nos. 0048 to 0054, FIG. 2)
A professional image switching apparatus is very expensive and a cost thereof is considerably increased by only increasing the number of circuits and increasing channels among the circuits. For this reason, it is requested that such image switching apparatus should become available in a variety of purposes and also it is requested that a cost thereof should be decreased by decreasing the number of circuits.
However, in the image switching apparatus described in the above-described Cited Patent Reference 1, when only video signals of channels (for example, one or two channels lesser than the number of the image processing units 51 and on which simple effects were performed are generated, only a part of the image processing units 51 is used and other remaining image processing units 51 are not available in actual practice. As described above, the image processing units 51 which are not available should be provided and hence it is difficult to decrease a cost of such image switching apparatus.